/Engine/Source/Runtime/RenderCore/Public/IRenderCaptureProvider.h
Capture the next full frame of rendering information. Currently any capture details (number of frames etc.) must be set up by CVars exposed in the underlying capture tool. Call from main thread only.
void CaptureFrame ( [FViewport](API\Runtime\Engine\FViewport) * InViewport, uint32 InFlags, [FString](API\Runtime\Core\Containers\FString) const & InDestFileName )